How to divide an object with Blender 2.8
I am showing you on a cube.
If you are loop cutting from exact center, that is Ctrl + R and Right Clicking mouse button to exit sliding.
In Edit Mode:
Go to face select mode.

and select the faces on the other half.

Now press P and seperate by Selection.

Go to Object Mode(by pressing Tab)and select any half of cube and Press G to Grab and move.



  This same method works on Blender 2.79 too.


Now cube is divided into two different parts! Enjoy.